SUMMARY: update Compiler Explorer link

Compiler Explorer added "Compiler Overrides" [1], which for Rust
include setting by default the 2021 edition. Since `rustc` does
not allow that, the old link has stopped working.

Reported to Compiler Explorer at [2].

Link: compiler-explorer/compiler-explorer#5001 [1]
Link: compiler-explorer/compiler-explorer#5429 [2]
Reported-by: Dimitri Belopopsky <dimitri@belopopsky.com>
Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/288089-General/topic/CE.20link.20on.20rust-for-linux.20site/near/387667888
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

SUMMARY.md

@@ -83,6 +83,6 @@
 ## Other resources
 
   - [Bootlin's Elixir](https://elixir.bootlin.com/linux/latest/source/rust)
-  - [Compiler Explorer](https://godbolt.org/z/W4P36a9h9)
+  - [Compiler Explorer](https://godbolt.org/z/oM99voaPT)
   - [Rust Playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021)
   - [Rust `core` docs](https://doc.rust-lang.org/1.62.0/core/)